Woven hollow fiber double weft tape with knitted selvedge

ABSTRACT

A woven hollow tape, for use in exchange devices such as blood oxygenators and heat exchangers, having weft threads and hollow fibers as warp threads, formed as a double weft tape, in which one tape edge is formed as a knitted edge and the weft density is much less than that found in normal woven textile tapes, each weft being spaced apart from the adjacent wefts. The tape is produced by a weft insertion that takes place in a manner similar to that of a shuttleless ribbon loom, especially a needle ribbon loom, preferably using freshly spun hollow fibers. The resultant tape may have hollow fibers along both edges and may be used to form the appropriate products either with or without the weft threads which are easily removed as a result of the tape structure.

BACKGROUND OF THE INVENTION

The invention relates to a woven hollow fiber tape with weft threads andhollow threads as the warp threads. The invention also relates to amethod and a device for manufacturing the woven hollow fiber tape aswell as hollow fiber bundles composed of woven hollow fiber tapes.

A woven hollow fiber tape with weft threads and hollow threads as thewarp threads and a blood oxygenator manufactured therefrom are knownfrom EP-A2-0 089 122. This known woven hollow fiber tape is the typemanufactured on a so-called shuttle loom. The manufacture of such wovenhollow fiber tapes is very cumbersome and hence expensive. A furtherdisadvantage of hollow fiber tapes woven in this manner is that the weftthreads cannot be pulled out again as is frequently desired. Inaddition, this hollow fiber tape necessarily has a monofilament (solidfiber) on each side edge to protect the hollow fibers at the edgeagainst transverse forces and abrasion by the shuttle and to absorbtensile stresses. Such threads, however, make the manufacture of thehollow fiber tape more difficult and frequently cause problems in thefinished device. Processing this known woven hollow fiber tape into ablood oxygenator and the blood oxygenator itself likewise involvedisadvantages. One disadvantage of this known processing method to turna woven hollow fiber tape into a blood oxygenator is its considerableengineering cost. Thus, a special device is required for reversal whenthe woven hollow fiber tape is reversed at the ends of the winder toform the next hollow fiber layer, said device making the reversalpossible. In addition, the area of deflection of the hollow fibers whichthus results and cannot be used is considerable, resulting in a largepercentage of waste. This method also has the additional disadvantagethat the winding angle to the axis of the winder is only between 30° and90°. The length of the hollow fibers is then a multiple of the axiallength of the winder. This results in an increased pressure loss in theinterior (lumen) of the hollow fibers. In addition, if the winding anglebetween the axis of the winder and the woven hollow fiber tape is notmodified accordingly as a function of the number of layers, the lengthof the hollow fibers will increase with an increasing number of layers.This produces a nonuniform flow through the hollow fibers, somethingwhich is generally undesirable.

SUMMARY OF THE INVENTION

Hence, the goal of the present invention is to provide a woven hollowfiber tape which is less expensive to manufacture and can be employedmuch more diversely, the tape also permitting a design in which the weftthreads perform only a temporary auxiliary function when processing aplurality of hollow fibers (hollow fiber sheet), in other words, aprocessing aid. Another goal is to provide a simpler and more economicalmethod of manufacture to make a woven hollow fiber tape of this kind aswell as a device suitable for the purpose. Finally, another goalconsists of providing hollow fiber bundles which can be producedeconomically from woven hollow fiber tapes with a high material and/orheat exchange ability.

These goals are achieved by a woven hollow fiber tape with weft threadsand hollow threads as warp threads, designed according to the inventionas a double weft tape, by the method described below, by the devicedescribed below, and by the hollow fiber bundles described below.

Hollow fibers whose walls are completely or partially permeable tomaterials, in other words, are permeable or semi-permeable, and whichconsequently are suitable for material exchange, material separation,and/or material transfer, are frequently also referred to as capillarymembranes. Capillary membranes can be used in medical or technicalapplications. Typical applications for capillary membranes include, forexample, blood plasmapheresis, hemofiltration, electrodialysis,dialysis, oxygenation, reverse osmosis, ultrafiltration,microfiltration, pervaporation, etc.

The outside diameters of hollow fibers (capillary membranes) lie in thefollowing ranges, for example:

for dialysis, from 150 μm to 280 μm;

for oxygenation, from 150 μm to 500 μm;

for plasmapheresis, from 150 μm to 650 μm.

Hollow fibers with a wall that is essentially impermeable to materialsare frequently used for heat transfer, in other words, in heatexchangers. Hollow fibers with a (micro-)porous wall are used, forexample, for (micro-)filtration, membrane distillation, etc.

To make material and heat exchangers of this type, a plurality of hollowfibers is normally combined to form a hollow fiber bundle and thereby,preferably placed in a certain arrangement, to shape the flow areabetween the hollow fibers for the medium flowing around the outsides ofthe hollow fibers in such a way that, depending on the application ofsuch a hollow fiber bundle, specific requirements regarding momentum,heat, and material transport phenomena are met.

For example, in a capillary membrane oxygenator the blood flows betweenthe capillary membranes, that is, the latter have the blood flowingaround them externally. Capillary membranes are terminated by embeddingthem in such a way that their openings terminate in separate supply anddischarge chambers for the oxygen flowing through the capillarymembranes, their lumina. For gas exchange between the blood and theoxygen through the walls of the capillary membranes it is thereforeadvantageous to arrange the capillary membranes in such a way that ahigh oxygen/carbon dioxide exchange is achieved and only a smallblood/membrane contact area is required.

These and other requirements are met by the invention in an economicaland technically superior fashion. For an improved understanding of theterminology employed here and the technology of the preferredmanufacturing method and the device suitable for the purpose, the readeris referred to the following patents, which also serve for disclosure ofthe invention: U.S. Pat. No. 4,399,841, U.S. Pat. No. 4,761,864, U.S.Pat. No. 3,605,225, U.S. Pat. No. 4,006,758.

The term "double weft tape" will be understood in the context of thepresent invention to be a woven tape in which a double weft insertionhas taken place, in other words, two weft threads are inserted per weftinsertion, producing so-called double wefts. Double weft insertion intextile fabrics is a type of rib weave and, with the usual high weftdensity, results in double-weft rib (grain); for this reason it is alsoreferred to as grain weave. In the manufacture of woven tapes on shuttlelooms, a so-called true selvage is produced on both sides of the tape.Shuttleless weaving methods, on the other hand, make it possible tomanufacture woven tapes in which at least one edge of the tape is notmade in the form of a true selvage. One embodiment of a non-true selvageis the knitted edge, which is also selected as an especially preferredembodiment of the woven hollow fiber tape according to the invention.The knitted edge is produced, for example, in the shuttleless weavingmethod in which the weft thread is laid as a thread loop through theshed (inserted) and the laterally projecting weft thread loop is knittedinto a stitch (crocheted or stitched), in other words, the weft threadis tied to itself. This process is also referred to as the formation ofa knitted edge by stitching the weft thread. Such a knitted edge, ifdesired, can be tightened further (rippled), so that the weft thread caneasily be pulled out again completely and removed. However, it is alsopossible with this technique to tie off the weft thread loops, forexample using an auxiliary thread, or to fasten them, for example bygluing, so that rippling is not possible. Tying off or stitching isusually performed using a knitting needle.

The term "weft density" is the number of weft threads per unit length ofa woven tape. In the hollow fiber tape woven according to the invention,it is preferably much less than in normal woven textile tapes, wherebyfirstly, a loose, woven hollow fiber tape with sufficiently dimensionedintermediate spaces for a low-pressure loss flow around the hollowfibers is produced, in which the hollow fibers, however, are arranged atdefinite mutual intervals, in other words, in the arrangement describedabove for high material and/or heat transfer ability. The low weftdensity also provides in advantageous fashion a high manufacturing speedfor the woven hollow fiber tape. The term "low weft density" refers, forexample, to one that has 3 to 35 mm and especially 10 to 15 mm per weft,but in any case one in which the adjacent weft threads do not lie closetogether or do not touch one another. The weft threads, therefore, runmeanderwise or form a zigzag line, a sawtooth line, or the like, andform an angle with the warp threads which is smaller on the average than90°, for example, 15° or 30° or 45°.

In the woven hollow fiber tape according to the invention, the weftthreads are preferably made of monofil or multifil endless thread whichis unwound during manufacture, for example, continuously from a bobbin.The weft threads can be much finer than the hollow fibers. The weftthreads can also be made of threads twisted in different ways. Inspecial applications, it may be advantageous for the weft threads to bemade of the same material as the warp threads (hollow fibers).

It is also possible to use as weft threads those which themselvespossess a property that performs material exchange, which therefore areable, for example, to absorb or adsorb a substance from the mediumflowing around the hollow fibers, or to give a substance off to it,possibly with a delay or slowly. The weft threads can also be arrangedor made such that they contribute to the formation of turbulence orlaminar mixing. The weft threads can also be inserted in such a way thatthey produce an undulation of the hollow fibers (warp threads), whichcan result in an increase in the ability to transfer materials and/orheat.

The woven hollow fiber tape can contain, for example, 3 to 300 hollowfibers as the warp threads, with one preferred embodiment containing 15to 40 hollow fibers. The width of the woven hollow fiber tapeessentially reflects the diameter of the hollow fibers. A width of 10mm, mentioned here only as an example, has proven to be highly suitablein the subsequent processing of the woven hollow fiber tape onto bobbinsand into hollow fiber bundles.

The woven hollow fiber tape can also have hollow fibers with differentproperties for the warp threads. Typical properties of hollow fibersused for different purposes include, for example, wettability(hydrophilia, hydrophobia), permeability, UF rate, etc. The woven hollowfiber tape can also have hydrophobic and hydrophylic hollow fibers init, or hollow fibers with different permeabilities, each of which servesa different purpose. It can also include hollow fibers that promotematerial exchange and those which serve for simultaneous heat transfer.Such different hollow fibers can be present in any mixing ratios thatcorrespond to the specific requirements.

In addition, the woven hollow fiber tape can also have a number ofthreads as warp threads which, for example, have a supporting functionor increase the tensile strength of the hollow fiber tape and acceptpossibly high tensile stresses during subsequent processing of the woventape. Such threads can also have adsorptive or desorptive properties andremove materials from the medium surrounding them and the hollow fibers,or give off materials to this medium, possibly in a controlled manner.

Threads with precisely adjustable and triggerable shrinking propertiescan be used, for example, to crimp the hollow fibers in a desiredfashion at a given point in time, for example during a certainprocessing step.

The high order of the woven hollow fiber tape, therefore, makes itpossible, for example, to make a woven hollow fiber tape for an IVfilter with venting, in which one or more hydrophobic porous hollowfibers for venting are arranged along at least one edge. The hollowfibers can then be embedded in such a way that, because of the highorder within the woven hollow fiber tape, the hydrophobic edge fiberswhich bring about the venting are separated from the hydrophylic hollowfibers which promote filtration, in the embedding area by a suitabledistributor head.

The warp and/or weft threads can also perform a function as catalyst,enzyme storer, heat storer, heat dispenser, and the like and be providedfor this purpose as hollow fibers or other fibers. If hollow fibers areused for this purpose as warp threads, they can be sealed at their endsand the resultant encapsulated interior (lumen) can be filled with asuitable substance. With such a combination of different functions, thewoven hollow fiber tape offers the advantage that it favors a uniformlyrepeatable local order.

The manufacture of the woven hollow fiber tape proceeds similarly to ashuttleless ribbon loom, as far as the weft insertion is concerned. Ithas been found especially advantageous in this regard when a device isused for this purpose that it is similar to that usually employed inneedle ribbon looms. In this method, the shuttle is inserted verycarefully so that no additional special monofilaments need to beprovided to protect the hollow fibers along the side edges of the hollowfiber tape. It is also possible, however, to use a device like thatusually employed in rapier looms.

In the method according to the invention for manufacturing woven hollowfiber tape, the drive for the transport of the warp threads (hollowfibers) and the drive for the device for inserting the weft threads arepreferably decoupled or decouplable. This has the advantage that theweft thread density can be altered independently of the transport speedof the warp threads, or the weft insertion can be shut off completelyeven without interrupting the transport of the warp threads, which ishighly advantageous when starting or changing the shuttle insertiondevice. Ordinary ribbon looms, such as needle ribbon looms, do not offerthis advantage and are also not designed for a high weft density. Thetransport speed for the warp threads is so low that these machines arenot suitable either for making hollow fiber tapes with much smaller weftdensities or for integration into the manufacturing process for hollowfibers. Use of the known needle ribbon looms results in hollow fibertapes with the usual high weft density and also allows only processingof hollow fiber bobbins. However, an advantage is also gained in that,with a suitable design of the knitted edge of the hollow fiber tapes,the weft threads can be pulled out again at a later point in time, sincea double weft hollow fiber tape is also produced in this case.

One important advantage, however, is achieved in looms of this kind,especially when, as described above, the drive for the transport of thewarp threads and the drive for the insertion of the shuttle can bedecoupled or are decouplable. Hence, the merely optional couplingmentioned in the latter case of the two drives can also be performedmechanically or electrically.

When manufacturing the especially preferred embodiment of the hollowfiber tape with a low weft density, the otherwise normal reed can beeliminated, by which the weft threads are beaten onto the weft threadsthat have already been woven. This in turn results in a simplificationof the manufacturing method and of the device suitable for the purpose.

Shedding can be performed in such a way that every second hollow fiberis raised as in a plain weave. When using more than two shedding devicesand/or appropriately designing the shedding devices, other types ofweave can be produced, for example, those with a float weave and thelike, in which the shed is formed for example as in satin or body weave.

For simplified shedding, even in the method according to the invention,it is also possible to use ordinary heddles with healds. However, it ismuch more advantageous to use for shedding, reeds that are open at thetop (or bottom) with thread heddles of different depths. Reeds of thiskind or similar devices can be provided with a device by which thethread heddles can subsequently be closed from above (or from below),for example, covered.

A rotating device or one that can be rotated backward and forward,similar to a camshaft, can also be used for shedding, in which the"cams" raise the hollow fibers to shed. When using reeds, the latter canbe arranged to be moved like the heddles of ordinary looms; however,they can also be mounted on a common rotatable shaft so that sheddingtakes place in a manner similar to the device resembling a camshaftdescribed above. It is also possible to guide more than one threadthrough one heald or one thread heddle (when using reeds).

Such reeds which are open at the top (or bottom) or similar devices forshedding can be inserted advantageously not only into a resting warpthread group from below (or from the top or from the side) but into onethat is moving, considerably facilitating the initiation of the weavingprocess on resting warp threads and making it possible for the firsttime to work with moving warp threads.

The continuous hollow fiber manufacturing process is not interrupted asa result, and if the loom breaks down a spare unit can be insertedwithout interruption. Maintenance and replacement of weaving equipmentis also possible without interrupting or influencing the manufacture ofhollow fibers.

The embodiment of the method for manufacturing a woven hollow fibertape, in which the activity is performed without a reed and withdecoupled or decouplable drives for the warp and weft threads, asdescribed above, and with reeds open at the top (or at the bottom) orsimilar devices for shedding, is therefore especially suited for beingintegrated into the manufacturing process for the hollow fibers. Thisability, which did not exist in the previously known methods formanufacturing a woven hollow fiber tape, constitutes an importantadvantage and a significant technical advance which consists, forexample, in reducing the method steps and hence the expense inmanufacturing woven hollow fiber tapes, since it is no longer necessaryas formerly to wind the hollow fibers initially onto bobbins and onlylater process them into woven hollow fiber tapes.

Thus, the method in its preferred embodiment can also be performed onhollow fibers which are still wet, damp, or generally unfinished, inother words, even before the extraction of solvents, before drying, orat another point in the manufacturing process. This is possible becausehollow fibers generally reach a basic strength immediately aftercoagulation or phase separation, which makes it possible to transportthe hollow fibers through the weaving device according to the inventionin which weft insertion takes place in a very careful manner. In thisway, even at a very early stage in the manufacturing process, a fibertape, namely a woven hollow fiber tape, can be manufactured whichbehaves much more favorably during the process and is much easier tohandle. Thus, the tangles, sags, or rideovers (undesired threadscrossing over one another), which are frequently observed, for example,on or between deflecting rollers, in thread sheets with hollow fibersrunning parallel to one another are avoided. It is also possible toimprove the mutual spacing in the hollow fibers in this fashion, makingit as small as possible initially, which can be utilized for a higherdegree of implementation of existing facilities or results in muchsmaller (narrower) machines with the same production output, but stilllarge enough for a good flow around the hollow fibers in method stepssuch as extraction, washing, drying, etc. A hollow fiber spacing in therange from 0.2 d to 1.5 d (d=hollow fiber outside diameter) has provenadvantageous for most applications. In addition, the risk of threadsbreaking during the process is reduced and hence the processability ofhollow fiber sheets is considerably improved.

The method according to the invention can also be integrated into themanufacturing process, with the hollow fibers being produced by meltspinning.

The shuttleless weaving method according to the invention allows(especially when the weft insertion is performed in a manner similar tothat in a ribbon loom) high processing speeds for hollow fibers, i.e.hollow fiber sheets, into woven hollow fiber tapes according to theinvention, with the processing speed being limited by the technicallyfeasible weft frequency. The ratio of the weft frequency to the warpthread speed produces the weft density, in other words, the distancebetween the individual weft threads. When the speed at which the hollowfibers are brought to and carried away from the weft insertion devicedecreases, while keeping the weft frequency constant, a resultantincrease in weft density is produced and vice versa. Weft density shouldbe kept as low as possible for cost reasons but so that the technicalrequirements are met in every case. Here again, an optimum can bedetermined by simple tests. The method according to the invention isconsequently employed preferably at processing speeds of the hollowfibers in the range from 10 to 80 m/min, with a weft frequency in therange from 30 to 200 Hz.

The woven hollow fiber tape according to the invention can be processed,for example, into bobbins, hollow fiber bundles, or other hollow fiberarrangements.

Frequently, multifil bobbins are desired for manufacturing certainhollow fiber structures, in other words bobbins onto which apredetermined number of hollow fibers has been wound. This is frequentlydesirable when the number of hollow fibers in the finished structure(e.g. IV filter) is relatively low and so small a number of hollowfibers can be wound onto a bobbin. When a woven hollow fiber tape with acorresponding number of hollow fibers is used, it is no longer necessaryto fit together a plurality of hollow fibers unwound from differentbobbins to form multifil bobbins.

When unwinding the multifil bobbins previously in normal use, pinchedthreads or sags were frequently encountered, which led todiscontinuities or broken threads. These problems can be avoided withmultifil bobbins in which the hollow fibers are wound as woven hollowfiber tape. Frequently, however, the weft thread is undesirable in thefinished product, and there may be many different reasons for this. Thewoven hollow fiber tape according to the invention also offers anotherimportant advantage, namely the possibility that the weft thread, with acorresponding tie (stitching), after unwinding the hollow fiber tapefrom the bobbin, can be pulled out immediately before further processingof the hollow fibers. This provision opens up a much broader range ofapplications for the woven hollow fiber tapes according to theinvention, especially when the warp thread has only a temporaryauxiliary function.

The woven hollow fiber tape according to the invention can also be woundinto hollow fiber hanks, from which hollow fiber bundles of the desiredlength can then be cut. For this purpose a method or device can be used,for example like those described in U.S. Pat. No. 4,681,720.

The processing of the woven hollow fiber tape according to the inventioninto hollow fiber bundles, however, can be performed in a different way,whereby especially preferred manufacturing methods for hollow fiberbundles and the hollow fiber bundles manufactured by this method will bedescribed below and explained in greater detail with the aid of thefigures. The so-called packing density, in other words the ratio of thevolume filled with hollow fibers to the total volume, can be set to therange from 30 to 60% in a device made from hollow fiber tapes accordingto the invention (dialyzer, oxygenator, heat exchanger, etc.).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail with reference tothe drawings, wherein:

FIG. 1 shows a section of a first embodiment of a woven hollow fibertape;

FIG. 2 shows a section of a second embodiment of the woven hollow fibertape with an increased and angled spacing between wefts;

FIG. 3 is a view of the weft insertion device;

FIG. 4 a perspective view of the device for shedding;

FIG. 5 is a hollow fiber bundle made of woven hollow fiber tapes;

FIG. 6 is a hollow fiber structure made of woven hollow fiber tapes; and

FIG. 7 portrays a cross-section of a hollow fiber bundle made of wovenhollow fiber tapes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a section through a woven hollow fiber tape, consisting ofhollow fibers 1 as the warp threads and weft threads 2. The weft threads2 in this embodiment of the woven hollow fiber tape run essentiallyparallel to one another and perpendicularly to the hollow fibers (warpfibers) 1, whereby the double wefts are clearly evident. The left-handedge of the woven hollow fiber tape in the drawing is designed as a trueselvage. The right-hand tape edge, on the other hand, is designed as aknitted edge, with the laterally projecting weft thread loops beingknitted together (stitched) or, in other words, tied to themselves. Aknitted edge of this kind can be tightened further if desired. The lowweft density is also clearly apparent, which results from the fact thatthe adjacent weft threads 2 do not contact one another but are arrangedat a distance from one another, which is a multiple of the thickness ofthe weft threads. According to the present invention, this arrangementcan also be designed a meander-shaped pattern of weft threads.

FIG. 2 shows the section of a woven hollow fiber tape in which weftthreads 2 form a zigzag line and hence an angle smaller than 90° withthe hollow fibers (weft threads) 1. The weft density is even less thanin the woven hollow fiber tape shown in FIG. 1. With regard to the otherfeatures of this embodiment of the woven hollow fiber tape, the readeris referred to the description of the embodiment of the woven hollowfiber tape shown in FIG. 1.

FIG. 3 shows a weft insertion device which resembles the typeconventionally used in needle ribbon looms, and which is preferably usedin the method and device for manufacturing the woven hollow fiber tape.Hollow fibers 1 run through the loom in the direction indicated by arrow3. The device consists of the inserting element (needle) 4, with eye 5for the weft thread (not shown), which is permanently attached toretaining arm 6. Retaining arm 6 is permanently attached to the shaft 8which rotates back and forth, consequently executing a movement asindicated by arrow 7. The movement of retaining arm 6 causes needle 4 toperform a corresponding movement between two end positions as indicatedby arrow 10. In the drawing, needle 4 is shown in its left-hand (in theplane of the drawing) end position. The right-hand (in the plane of thedrawing) end position is located at the right above deflecting rod 11,as indicated by the tip 4a of needle 4 which is shown in dashed lines.Deflecting rod 11 is mounted perpendicular to the plane of the drawingand hence perpendicular to the plane in which the hollow fibers (warpfibers) 1 pass through the active area of the loom. Another part of theloom is retaining element 9 for the weft thread (not shown), which ismounted essentially perpendicular to the plane of the drawing, in otherwords perpendicular to the hollow fiber tape plane, and can be moved upand down. To stitch the weft thread loops on the right-hand hollow fibertape edge at the right (in the plane of the drawing), the knittingneedle (tongue needle) 12 is used which is mounted parallel to thelengthwise direction of the hollow fiber tape and can move back andforth, as indicated by arrow 13. The operation of the weft insertiondevice shown in FIG. 3 essentially corresponds to that known from needleribbon looms, and therefore need not be described in greater detailhere. The reed, as is usually found in needle ribbon looms, is missingfrom the device as shown, however.

FIG. 4 shows two reeds 14 and 15 open at the top for shedding. Reeds 14and 15 have thread heddles 18 and 19 of different depths, with threadheddle 18 being approximately twice as deep as heddle 19. Reeds 14 and15 can be moved up and down, as indicated by arrows 16 and 17. Threadheddles 18 and 19 of reed 14 are mounted staggered opposite threadheddles 18 and 19 of reed 15, in other words looking in the direction oftravel of the warp threads, a thread heddle 18 of reed 14 and a threadheddle 19 of reed 15 occur sequentially. The shed is shown only by thehollow fibers (warp threads) drawn on both sides of reeds 14 and 15. Inthe embodiment of reeds 14 and 15 shown here, each deep thread heddle isfollowed by a thread heddle 19 which is a little less deep, so that theshedding takes place in the same way as in plain weaving. However, it isalso possible to provide a different arrangement of the thread heddles,for example such that two deep thread heddles 18 follow one or two lessdeep thread heddles 19, and so on. Thread heddles 18 and 19 of the reeds14 and 15 shown, after insertion of hollow fibers 1, can also be coveredto prevent hollow fibers 1 from jumping out during weaving. The openreeds 14 and 15 shown can, in the arrangement shown, be brought in andout advantageously from below, even with the warp thread sheet inmotion, whereby the weaving process on a running warp thread sheet canbe initiated or discontinued at any time, of course before or after aplanned covering of thread heddles 18 and 19. With the reversearrangement of reeds 14 and 15, the movement into and out of the warpthread sheet takes place from above.

FIG. 5 shows a hollow fiber sheet made of woven hollow fiber tapes inwhich the ends of hollow fibers 1 are embedded in head plates 3. Usuallythe hollow fiber ends are embedded by spinning them into a curablepotting compound. After curing of the potting compound, as much materialis removed endwise as is necessary to expose the open ends of hollowfibers 1, so that a throughflow in the chamber (lumen) of hollow fiber 1is possible. This can be done at one end, for example, in so-called deadend filters, or at both ends, as for example in dialyzers, oxygenators,heat exchangers, etc. For legibility, only three hollow fiber tapes areshown, arranged in layers around a core 4 (e.g., a core tube) in such away that hollow fibers 1 of adjacent layers form layers with an angle αwhich is preferably ≦30° and in special cases can also be only about 1°.The fact that weft threads 2 are present means that even at such smallangles of intersection the overlap is maintained and the hollow fibersof one layer do not, as is unavoidable in hollow fiber tapes withoutweft threads, slip into the spaces of an adjacent layer, whereby adisorderly hollow fiber bundle would result, with hollow fibersessentially arranged parallel to one another and touching one another aswell, which would result in an extremely inadequate surrounding flowdistribution. The angle which hollow fibers 1 form with the lengthwiseaxis of the bundle (not shown) is about α/2.

A hollow fiber bundle made of woven hollow fiber tapes can also beformed without a core. Thus, for example, two layers of woven hollowfiber tape can be formed, with the woven hollow fiber tapes beingarranged parallel to one another inside a layer, but forming an angle αwith the hollow fiber tapes of the other layer. The two layers can thenbe wound up in a spiral even without a core to form a hollow fiberbundle. It is understood, of course, that initially more than two layerscan be formed when the hollow fibers of adjacent layers form an angle ofintersection α and that this multilayer structure can then be wound upspirally, for example around a core, to form a hollow fiber bundle.

FIG. 6 shows in perspective view a hollow fiber structure of wovenhollow fiber tapes 1, 2 formed by the simultaneous meanderwise layingdown of two woven hollow fiber tapes 1 and 2, whereby the hollow fibers1a and 2a extending in a lengthwise direction of such a woven hollowfiber tape intersect at right angles in the finished hollow fiberstructure. This type of construction is termed plaiting for textile websand the like. It can be done manually or by machine. Further processingof the hollow fiber structure to a hollow fiber module can beaccomplished as follows: the deflecting points (bends) of the wovenhollow fiber tapes 1 and 2 can be embedded along the four long sides ofthe hollow fiber structure in a suitably dimensioned potting compoundplait and the hollow fiber spaces (lumina) are then exposed. A hollowfiber module of this kind makes it possible to enable three fluids toparticipate in a material and/or heat exchange, with the first fluidbeing guided through hollow fibers 1a, the second fluid through hollowfibers 2a, and the third fluid externally around hollow fibers 1a and2a. It is also possible, however, to punch e.g. round segments out ofthe multilayered structure and process these further individually or inthe punched-out multilayer structure, in other words the hollow fiberends can be mixed into a curable potting compound.

FIG. 7 shows a portion of the cross section of a hollow fiber bundlemade of woven hollow fiber tapes in which hollow fibers 1 are arrangedessentially parallel to the lengthwise axis of the bundle, with thewoven hollow fiber tapes being formed into partial bundles with anycross section, essentially irregular, in such a way that hollow fibers 1are distributed essentially without gaps uniformly over the crosssection of the hollow fiber bundle. The hollow fiber bundle, therefore,consists of a plurality of woven, essentially parallel woven hollowfiber tapes. The limit lines 20 shown of a shaped woven hollow fibertape serve only for clarification; for example, there is only animaginary and not a real limit between the individual partial bundles.Despite this arrangement, the presence of the weft threads (not shown)means that hollow fibers 1 will not slide into the spaces betweenadjacent hollow fibers 1, but that a relatively loose bundle of hollowfibers through which flow can occur smoothly is formed. In thisarrangement of woven hollow fiber tapes as well, it is possible toprovide a core (core tube) and to arrange the woven hollow fiber tapesessentially without gaps uniformly over the remaining annular crosssection and to distribute them there.

What is claimed is:
 1. A woven hollow fiber tape having two longitudinaltape edges, comprising: weft threads and hollow fibers as warp threads,wherein the weft threads form a different selvage weave structure alongeach longitudinal tape edge and wherein for each longitudinal tape edgethe warp thread located at the outermost position thereof is a hollowfiber.
 2. A woven hollow fiber tape according to claim 1, furthercomprising one longitudinal tape edge having a knitted edge.
 3. A wovenhollow fiber tape according to claim 1, wherein the weft density is inthe range of 28 to 333 wefts per meter.